1. Field of the Invention
This invention relates to a magnetic recording and reproducing system using a so-called giant magnetoresistive film, and in particular, to a magnetic recording and reproducing device having a high recording density.
2. Description of the Related Art
In the related art, a magnetic field sensor comprising at least two ferromagnetic thin films separated by an intermediate layer is described in Japanese Patent Laid-Open No. 2-61572. The magnetic field sensor is made of material with the magnetization directions of both the ferromagnetic thin films becoming antiparallel in one direction depending on whether or not the effect of an external magnetic field exists, and detects an external magnetic field at high sensitivity on the basis that electron scattering depending on the spin direction occurs on an interface between the ferromagnetic layer and the intermediate layer.
Also, a magnetoresistive element comprising a multilayered film comprising a ferromagnetic film having the magnetoresistance effect and a metal conductor thin film having high electric conductivity laminated on each other is described in Japanese Patent Laid-Open No. 2-23681.
Further, a magnetic sensor using a so-called giant magnetoresistive film comprising a first ferromagnetic film and a second ferromagnetic film between which a nonmagnetic layer is sandwiched is described in EP490608A2. The magnetization directions of the first and second ferromagnetic films of the giant magnetoresistive film are at right angles or orthogonal to each other when no external magnetic field is received (zero magnetic field). When an external magnetic field is received, a resistance change occurs on the giant magnetoresistive film because the first and second ferromagnetic films differ in magnetization rotation direction. To detect an external magnetic field, an electric current is made to flow into the giant magnetoresistive film for detecting a resistance change. The necessity of paying attention to the direction of the current flowing into the film at this time is described in EP490608A2.
Particularly, those skilled in the art focus on the magnetic sensor using the giant magnetoresistive film as described in EP490608A2 because it provides high detection sensitivity compared with conventional magnetic sensors using single layer magnetoresistive film.
As described above, the magnetic sensor using the giant magnetoresistive film as described in EP490608A2 provides high detection sensitivity compared with magnetic sensors using a single layer magnetoresistive film, but if an actual magnetic recording and reproducing device is constructed, a high detection sensitivity which is expected in theory, cannot be provided, and no practical machine has yet been implemented.